The industry standard method of refuelling large diesel powered equipment in the mining, railway, and earthmoving industries has incorporated dry-break fluid couplings designed to transfer diesel fuel from a dispensing point into the fuel tank onboard the equipment. An integral component of this system is the specialised vent fitted to the tank being refuelled. This vent fulfils a number of key roles, including:                Free discharge of air from the tank during the refuelling process, at fuel levels under the level at which the vent valve is closed.        Closure of the main vent passage once the fuel level within the tank reaches a certain level on the vent. This essentially seals the tank allowing it to be pressurised as fuel continues to enter the tank.        Free-to-air passage of pressurised air from within the tank to atmosphere via a bleed hole within the vent, allowing the tank to gradually depressurise at the completion of the refuelling process.        Discharge of pressurised air and fuel from the tank through an emergency pressure relief valve within the vent, in the event the tank becomes over-pressurised.        Free intake of air into the tank through the vent as fuel is drawn from the tank.        
The equipment or tanks onto which such refuelling equipment is installed includes mining equipment, and other plant used in dirty and dusty environments. Recent research by a number of large mining companies and engine manufacturers has identified the many advantages in maintaining stringent standards of contamination control of fuel, oils, and other vital fluids. One of the key routes for contamination Ingress into a fluid is via the tank vent. Typically such vents have incorporated no air filtering mechanism, although this practice is steadily changing as contamination control strategies are enforced.
The basic function of the vent in the refuelling process remains the same as quick-fill vents used within the market for many years now, such as that detailed in the applicant's Australian patent no.s 586028 and 726581.
With respect to the fitment of air filtration to these quick-fill vents, mining equipment OEM's have installed remote mounted air filters and desiccant elements to tank vents to remove airborne contaminants and moisture from air entering the tank. However these systems do not offer the level or degree of filtration necessary to comply with modern contamination control standards, i.e. the micron rating of the air filters is too coarse. In response to more stringent filtration standards, filtered vents have been introduced onto the market, which incorporate a “spin-on” style generic air filter element which offered the degree of filtration necessary. It is understood that all incoming and outgoing air passes through the filter element, whereas air and fuel exhausted from the integral pressure relief valve, bypasses the filter element. Further, the intake ports of the filter element are directly exposed to the atmosphere, and thus exposed to rainfall and wash-down water.